Abstract

The three omega method has proven to provide accurate and reliable measurements of thermal conductivity of thin films and other materials. However, if the films are soft and conductive, conventional methodologies to prepare samples for the measurement technique are challenging and often unachievable. Various modifications to the sample preparation to employ this technique for soft conducting films are reported in this paper including the use of shadow masks for metal heaterdeposition and a process for preparation of low temperature insulating films required between film and heater. In this work, thick and ultrathin films of polyaniline as well as a thin film of low temperature plasma enhanced chemical vapor deposited as a function of temperature were measured. Though not considered a soft material, the silicon dioxide film was utilized for comparison with previous data. Results indicate that the film exhibits a thermal conductivity slightly lower than others’ data [S. M. Lee and D. G. Cahill, J. Appl. Phys.81, 2590 (1997);H. Yan et al., Chem. Lett.2000, 392;H. Yan et al., Anal. Calorim.69, 881 (2002);J. E. de Albuquerque et al., Rev. Sci. Instrum.74, 306 (2003)], which is likely due to the low temperature processing conditions that results in additional disorder in the film. The polyanilinefilms exhibit an increase in thermal conductivity with temperature, which is largely due to increasing heat capacity. The thick filmthermal conductivity is many times the value corresponding to the thin film, which is likely due to significant phonon boundary scattering present in the ultrathin film.

Received 22 August 2006Accepted 24 January 2007Published online 18 April 2007

Acknowledgments:

The authors would like to thank Professor Scott Huxtable of Virginia Tech. for discussions and valuable suggestions. This manuscript is based upon work supported by the National Science Foundation under Grant No. CTS-0448881.

Article outline:I. INTRODUCTIONII. OVERVIEW OF THE THREE OMEGA TECHNIQUEIII. EXPERIMENTA. Film synthesisB. Sample preparation for the three omega methodIV. RESULTS AND DISCUSSIONV. CONCLUSIONS